The invention relates to a process for the production of molten pig iron or of steel pre-products from particulate ferrous material, in particular pre-reduced iron sponge, as well as for the production of reduction gas in a meltdown gasifier, wherein a fluidized-bed zone is formed by coke particles upon the addition of coal and by blowing in oxygen-containing gas by means of nozzle pipes penetrating the wall of the meltdown gasifier, into which the ferrous material to be reduced is introduced, as well as to an arrangement for carrying out the process.
A process of this kind is described in U.S. Pat. No. 4,317,677, wherein the oxygen-containing gas or pure oxygen is blown in above the metal sump formed or above the slag layer covering the same, through a ring of nozzle pipes penetrating the wall of the meltdown gasifier. In this manner, a fluidized bed of coke particles with a high-temperature zone in the lower region is produced. The particulate ferrous material, in particular pre-reduced iron sponge, and the lumpy coal are supplied from top through charging openings in the hood of the meltdown gasifier. The falling particles are braked in the fluidized bed and the ferrous particles are reduced and melted in falling through the coke fluidized-bed. The melted metal covered by slag, collects on the bottom of the melt-down gasifier. Metal and slag are drawn off through separate tap openings.
With the known process, difficulties may aries if coals are used having an elevated sulfur content. Usually, the sulfur content of metallurgically usable coals amounts to 0.7 to 1.2%, but sulfur contents of up to 2% may also occur. Therefore, with processes in which, by degassing such a coal, reduction gas is produced, which is used for pre-reducing in a combined pre-reduction - meltdown gasifying plant, it may happen that the reduction gas has considerable sulfur content. About one third of the sulfur contained in the coal is found in the reduction gas and is bound to iron as FeS in a very great portion during pre-reduction in a reduction shaft.
In common metallurgy, metallurgical coke has a sulfur content of from 0.7 to 0.6%. With a blast furnace process, however, this sulfur largely remains in the slag and will not provoke an intensive sulfurization of the pig iron. However, if pig iron is produced on the basis of a direct coal reduction process, as is the case with the initially mentioned process, considerably higher sulfur contents will occur than with the blast furnace metallurgy.